This invention relates to an engine starter and, more particularly, to an engine starter having a pinion gear engageable with an engine ring gear of an internal combustion engine for starting it.
FIG. 1 illustrates one example of a conventional engine starter to which the present invention pertains. In FIG. 1, the engine starter comprises a housing 1 having contained therein an electric motor 2 having a rotary shaft 3 rotatably supported by sleeve bearings 4 mounted in the housing 1. The front end (the right-hand end in the figure) of the rotary shaft 3 is supported by a nose cone 5 of the housing 1 through the bearing 4. The nose cone 5 defines therein a substantially cylindrical space and has formed in its wall an opening 6 for the purpose which will become apparent later.
The engine starter also comprises a pinion gear 8 rotatably and axially slidably mounted on the rotary shaft 3 through a sleeve bearing 9. The pinion gear 8 is slidable along the rotary shaft 3 between an inactuated position illustrated in FIG. 1 in which the pinion gear 8 is rearwardly positioned and disengaged from an engine ring gear (not shown) and an actuated position in which the pinion gear 8 is moved forward and engages the engine ring gear (not shown) through the opening 6 in the housing 1. The pinion gear 8 has a cylindrical outer surface 10 which is surrounded by the cylindrical wall of the nose cone 5 of the housing 1 and defines an annular space 11 therebetween.
In order to unidirectionally transmit a rotation of the rotary shaft 3 to the pinion gear 8, a unidirectional clutch 14 is disposed behind the pinion gear 8 to mechanically couple between the pinion gear 8 and the rotary shaft 3. The unidirectional clutch 14 is slidable on the rotary shaft 3 and mechanically connected to the pinion gear 8 so that they move together in the axial direction. The unidirectional clutch 14 has a substantially cylindrical outer surface 15 which also is surrounded by the cylindrical wall of the nose cone 5 and an annular space 16 is defined therebetween.
The engine starter further comprises an electromagnetic unit 18 including a solenoid switch 19 for selectively energizing the dc electric motor 2 and for electromagnetically driving the pinion gear 8 together with the unidirectional clutch 14 between the forward, actuated position and the rearward, inactuated position through a shift lever 20.
With the conventional engine starter as above described, undesirable foreign matter such as dust and particles can easily enter into the interior of the nose cone 5 of the housing 1 through the opening 6. The foreign matter entered into the housing nose cone 5 are often caught between the bearing surfaces between the rotary shaft 3 and the bearing 4, degrading smooth sliding and rotary movements of the pinion gear 8. The foreign matter may also enter into the dc motor 2 or even into the switch unit of the solenoid switch 19 through the annular clearances 11 and 16 defined around the cylindrical outer surfaces 10 and 15 of the pinion gear 8 and the unidirectional clutch 14, respectively. Such foreign matter may prevent the dc motor 2 and the switch 19 from properly operating. They also may damage the motor 2 and the solenoid switch 19. The foreign matter may also enter into the bearing surface between the rotary shaft 3 and the front bearing 4.